This report describes the iterative development of the Examining Data Informing Teaching (EDIT) measure. The EDIT is specifically designed to help researchers understand how teachers conduct ongoing assessments for individualization and use those assessments to guide instruction. The measure focuses on the processes the teacher uses for (1) planning what information to collect and how to do so, (2) collecting valid data, (3) organizing and interpreting the data, and (4) using the data collected to inform both overall and individualized instruction. The EDIT uses a multi-method approach in gathering evidence with checklists, ratings, and rubrics that describe how the teacher collects and uses assessment. EDIT raters review assessment and instructional planning documents, as well as video recordings of assessments and instruction. Raters also conduct a one-hour individual teacher interview. (author abstract)